How to Use an Autoclave

An autoclave is the most effective way of sterilizing medical and scientific equipment. While simple boiling in water at normal pressure kills most microbes and spores, it won't kill them all. An autoclave pressurizes the water to 1 atmosphere or 15 pounds per square inch, which in turn raises the water's boiling point. The autoclave then heats the water until boiling its new, elevated boiling temperature, at which point it is hot enough to kill all forms of life and thus sterilize the apparatus or equipment inside within 15 minutes.

Things You'll Need

Heat-resistant gloves

Twist the control knob for the drain valve on the autoclave, usually located on the bottom front of the machine, to the closed position.

Open the door on the autoclave and add hot water in the bottom of this opening, filling it to just below the front reservoir lip. On most machines this will take about 1 gallon of water.

Load the material to be sterilized into the shelf in the autoclave. Liquids in bottles should be 3/4 or less full, with lids slightly loosened. Clean petri dishes should be loaded in top side up, contaminated petri dishes get loaded agar side down, and instruments should be rolled in brown paper, which is then stapled to secure it.

Close the door of the autoclave and press down on the long handle to latch it securely.

Toggle the exhaust switch, located at the top middle of most machines, to slow exhaust if you are sterilizing materials that contain water, or fast exhaust for sterilizing apparatus.

Twist the timer to select the appropriate length of sterilization time. For small-volume machines this is 15 minutes, for machines containing over 1 liter of volume this is 30 minutes, and for larger machines with 1 gallon or more of volume you should select a 60 minute cycle. This starts the machine.

Wait until the timer and pressure indicator both read zero, and then open the door, taking care to keep your hands, arms and face away from the upper parts of the door where steam is emerging and might burn you.

Twist the drain valve control on the autoclave to the open position to empty the water.

Tips & Warnings

Be very careful when handling just-sterilized items; they are hot, and must be handled with sterile gloves to preserve their sterility.
Never open the door of the autoclave before the pressure gauge has come down to zero.